The present invention relates to building blocks and, more particularly, to interfitting construction units, or blocks, of precise height for constructing walls and buildings without mortar in the bed joints.
Walls and buildings constructed of, for example, concrete blocks require mortar at the bed joints, the horizontal interfaces between the blocks, in order to provide a level horizontal surface for each course of the blocks. This is due to the fact that concrete blocks and the like are manufactured in such a manner that the height of the blocks, from block to block and within each block, lacks adequate uniformity and precision. Most of the cost in constructing a wall of concrete blocks is in the labor needed to construct it, and it has been estimated that using mortar at the bed joints and levelling the blocks to make the horizontal surfaces of each course level and even accounts for about 70% of the labor cost.
Concrete blocks are made by filling a mold with concrete such that the bottom (or top) of the block, as the block will be positioned in a wall, coincides with the bottom. of the mold. Then, the bottom of the mold is moved downward from the rest of the mold; and the block is moved downward with the bottom of the mold until the block is free to be moved off the mold bottom. This is done every 6 to 7 seconds. With this standard method, there is very limited uniformity and precision in the height dimension of the resultant blocks. Industry standards require only that there be no more than xe2x85x9 inch, that is, +or xe2x88x92{fraction (1/16)} inch, variation of the height dimension in a block.
Without mortar, that is, with the blocks contacting the blocks of adjacent courses, at least portions of courses would not be level, and some of the blocks of a particular course would be higher than other blocks in the same course. In addition, due to such unevenness, there is misfitting of the blocks, which results in stress concentrations and, sometimes, failures. Also due to the unevenness, structures supported by such courses, such as beams, are contacted by only a portion of the area of the course which should contact the supported structure. There are spaces between the supported structures and other portions of the upper course which should contact the supported structures. As a result, stress concentrations are created in the course and in the supported structure, and the course or the supported structure sometimes fails.
By the present invention, building blocks are provided which are sufficiently uniform and precise in height that they can be used to construct walls without using mortar at the bed joints. The blocks can be stacked on one another with each block contacting the blocks above and below to produce walls having a precisely level and even upper surface. The blocks have integral interlocking formations formed in one piece with the blocks to enable each block to interlock with the blocks above and below. As a result, the labor and cost of building a wall of blocks is greatly reduced, and the construction process is made substantially faster.
In order to obtain the precise height, the blocks are molded with their height in a horizontal orientation. In other words, the blocks are molded in an orientation which is at a 90xc2x0 angle with respect to the orientation of the blocks when they are in a wall. The orientation during molding is also at a 90xc2x0 angle with respect to the conventional orientation for molding blocks. In the molding of the blocks according to the present invention, the surfaces which will define the top and the bottom of a block when the block is in a wall are in contact with the sides of the mold, which are fixed and which define a precise dimension between themselves. Since the blocks are slipped from the mold through the bottom and, thus, parallel to the sides of the mold, the distance between the surfaces which will be the top and the bottoms of the blocks in use that is, the height, is precise. The precision is retained as the blocks are slid down and out of the mold.
The blocks include an inner wall and an outer wall, each having four surfaces defining a rectangular perimeter, and a web connecting the inner wall to the outer wall. The blocks can also include one or more intermediate walls which are spaced from and generally parallel to the inner wall and the outer wall. The intermediate walls can be used for blocks having greater depth, the dimension from front to back. Where an intermediate wall is present, a first web connects the inner wall to the intermediate wall, and a second web connects the intermediate wall to the outer wall. Where two intermediate walls are present, a third web connects them. Further intermediate walls and webs can also be employed.
The webs each have a surface flush with end surfaces of the inner and outer walls, and the blocks are devoid of surfaces which lie off a plane containing the flush surfaces of the webs and which face the plane. As a result, the blocks can be formed in a mold and slipped from the mold in a direction perpendicular to the plane. The blocks can be made in a standard concrete block mold machine.
The cross sectional area of each web is made as small as possible while maintaining sufficient strength to hold together the walls of the blocks. In addition, the web is positioned at one end of the block, thereby defining a large open volume between the web and the opposite end of the block. Furthermore, the web is spaced from the top and the bottom of the block to define empty volumes above and below the web. As a result, the block defines vertical and horizontal passages adapted to receive reinforcing bars, insulation, and the like. These latter volumes cooperate with corresponding volumes in the blocks of adjacent courses to define larger horizontal passages.
Each web has a surface which is convex in a cross section generally parallel to the inner wall and the outer wall and concave in a direction transverse to that cross section, so that any water on the surface runs together and drips off. The webs can be molded in one piece with the inner wall and the outer wall or can be formed later. The webs can be made of the material of the inner wall and the outer wall, or can be made of a less heat-conductive material, such as a plastic, to limit heat conduction between the inner and outer walls. The minimal cross-sectional area of the webs also limits such heat conduction.
The interlocking formations are disposed to discourage moisture penetration and comprise recesses on the bottom surfaces of the inner wall and the outer wall and ridges on the top surfaces of the inner wall and the outer wall, or vice versa. The ridges have a shape complementary to the shape of the recesses, so that the ridges fit precisely into the recesses of a like block, and the recesses fit precisely with and support the ridges of a like block. The recesses and ridges have surfaces parallel to the top and bottom surfaces of the inner and outer walls to help bear loads.
The inner wall of the block has an outer surface defining a channel extending the entire length of the inner wall to accommodate wiring, especially in cooperation with the channels of other blocks. With this arrangement, there is no need to break through the wall and run wires through the interior of the blocks. Plateaus on opposite sides of the channel have flat surfaces for the mounting of wallboard without the use of furring strips.